The present invention relates generally to computer graphics processing, and, more particularly, to multi-buffering for operating multi-GPU graphics subsystems in a computer system.
In many computer systems with advanced graphics processing capabilities, the graphics processing subsystem includes a double buffering module. The double buffering module has two memory sections, i.e., a front buffer and a back buffer. The front buffer stores fully rendered images and supplies the images to a display driver. The back buffer stores images that are in the process of being rendered by a graphics processor. Once rendering to the back buffer is completed, and the front buffer image is in full display, the front and back buffers can be flipped. As such, the previous front buffer now becomes a back buffer and can store a new image as it is rendered, while the previous back buffer provides the newly rendered image it stored for display. The front and back buffers continually flip in this manner and at the same rate as that of the display refreshing (e.g., 50 Hz, 60 Hz, 75 Hz or 90 Hz). The buffer flipping has also to be in synchronization with the rendering speed, so that image tearing does not occur.
When a computer system employs more than one graphics processing unit (GPU), coordination among the GPUs and their buffers needs to use yet another technology or process, called bit-block-transfer (BLT), that is to combine two bitmap patterns from two buffers into one. FIG. 1 shows a two GPU system, with a master GPU does flipping and a slave GPU does BLT through a PCIe bus connection.
Double buffers with one for display and the other one for rendering, are only good for single GPU systems. When there is more than one GPU doing rendering, obviously there will be more rendered images than two buffers can handle, so that GPUs will be forced to halt rendering or idle from time to time, which then lowers the performance of the graphics subsystem.
It is therefore desirable for a multi-GPU computer system not to have idle time in any of its GPUs to fully appreciate the processing power offered by the multiple GPUs. What is needed is an improved method and system for enhancing the collective processing power of the computer system.